Avalanche Forecast

Issued: Feb 4th, 2018 4:00PM

The alpine rating is moderate, the treeline rating is considerable, and the below treeline rating is moderate. Known problems include Persistent Slabs, Wind Slabs and Loose Dry.

Tim Haggarty, Parks Canada

Jasper.

While we expect natural activity to drop off as recent storm and wind slabs settle out and the cold air takes over, the persistent slab problems still linger. Another storm in the forecast for Wednesday will provide a further test to the snowpack.

Summary

Weather Forecast

Warm, wet, pacific air is over-riding the cold arctic air that arrived to Jasper with a NorthWesterly flow Feb 3. A few cm of snow can be expected overnight Sunday before the cold air wins out again yielding a return to clear, mainly calm and cold through Tuesday. Forecasts call for this same pattern to bring another push of Pacific air Wednesday

Snowpack Summary

10-15 cm of new snow arrived with a Northerly flow Saturday. This sits over recent wind and storm slabs formed by 40cm of snow pushed around mainly by strong SW winds. Midpack persistent weak layers, mainly preserved Jan 7surface hoar down 40 to 60cm and the rotten Dec 15 FC sitting just below are still a concern but remain stubborn to triggering.

Avalanche Summary

Avalanche control on Wednesday along the Icefields Parkway produced numerous size 3 avalanches in the alpine, and many size 2-2.5 storm slab and loose avalanches at all elevations. Persistent slab avalanches were produced in the alpine where wind loaded areas provided enough of a load to trigger a step down to these mid-pack layers.

Confidence

Due to the number of field observations

Problems

Persistent Slabs

Control work on Wednesday produced several results on this layer, particularly in the alpine where storm slabs were able to entrain enough mass to step down to mid-pack instabilities. Field teams observed Whumpfing and moderate test results Sunday.

If triggered the storm slabs may step down to deeper layers resulting in large avalanches.

Aspects: North, North East, East, South East, South.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 3.5

Wind Slabs

Snow that began to accumulate last Sunday quickly settled into a touchy soft slab in many locations. In exposed areas, strong SW winds further developed these slabs midweek. 10-15cm of new snow that arrived Saturday and Sunday now hides these slabs.

If triggered the storm/wind slabs may step down to deeper layers resulting in large avalanches.Be cautious as you transition into wind affected terrain.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2.5

Loose Dry

The new snow that fell Saturday and Sunday has triggered a few slabs as it has sluffed off of rock faces or steep terrain. Consider the potential for this if you enter steep or confined terrain.

Avoid terrain traps, such as gullies, where the consequences of a small avalanche could be serious.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Feb 5th, 2018 4:00PM